Different Ways to Get Servlet Context ([email protected])

web-modules/jakarta-servlets-2/src/main/java/com/baeldung/servlet/context/ContextListener.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.ServletContextEvent;
+import jakarta.servlet.ServletContextListener;
+import jakarta.servlet.annotation.WebListener;
+
+@WebListener
+public class ContextListener implements ServletContextListener {
+
+    @Override
+    public void contextInitialized(ServletContextEvent sce) {
+        sce.getServletContext().setAttribute("contextPath", sce.getServletContext().getContextPath());
+    }
+
+    @Override
+    public void contextDestroyed(ServletContextEvent sce) {
+        sce.getServletContext().log("ServletContextListener destroyed");
+    }
+}

web-modules/jakarta-servlets-2/src/main/java/com/baeldung/servlet/context/GetServletContext.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.ServletContext;
+import jakarta.servlet.annotation.WebServlet;
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import java.io.IOException;
+
+@WebServlet(name = "get-servlet-context", value = "servlet-context")
+public class GetServletContext extends HttpServlet {
+
+    @Override
+    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws IOException {
+        ServletContext context = getServletContext();
+
+        // Next, we’ll fetch an initialization parameter from the context
+        String message = context.getInitParameter("message");
+
+        // Finally, we’ll send a response back to the user
+        response.getWriter().write(message);
+    }
+}

web-modules/jakarta-servlets-2/src/main/java/com/baeldung/servlet/context/ServletRequest.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.ServletContext;
+import jakarta.servlet.http.HttpServlet;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+
+import java.io.IOException;
+
+public class ServletRequest extends HttpServlet{
+
+    @Override
+    protected void doGet(HttpServletRequest servletRequest, HttpServletResponse servletResponse) throws IOException {
+        ServletContext context = servletRequest.getServletContext();
+
+        // Next, we’ll fetch an initialization parameter from the context
+        String message = context.getInitParameter("message");
+
+        // Finally, we’ll send a response back to the user
+        servletResponse.getWriter().append(message);
+    }
+}

web-modules/jakarta-servlets-2/src/test/java/com/baeldung/servlet/context/ContextListenerTest.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.ServletContext;
+import jakarta.servlet.ServletContextEvent;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import static org.mockito.Mockito.*;
+
+class ContextListenerTest {
+
+    /**
+     * Tests the contextInitialized method of ContextListener.
+     * <p>
+     * This test checks if the context attribute "contextPath" is correctly set to the context path
+     * obtained from the ServletContext during initialization.
+     */
+    @Test
+    void whenContextInitialized_thenSetsContextPathAttribute() {
+        // Arrange
+        ServletContext mockServletContext = Mockito.mock(ServletContext.class);
+        ServletContextEvent mockServletContextEvent = Mockito.mock(ServletContextEvent.class);
+        when(mockServletContextEvent.getServletContext()).thenReturn(mockServletContext);
+        when(mockServletContext.getContextPath()).thenReturn("/exampleContext");
+
+        ContextListener contextListener = new ContextListener();
+
+        // Act
+        contextListener.contextInitialized(mockServletContextEvent);
+
+        // Assert
+        verify(mockServletContext).setAttribute("contextPath", "/exampleContext");
+    }
+}

web-modules/jakarta-servlets-2/src/test/java/com/baeldung/servlet/context/GetServletContextTest.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.ServletConfig;
+import jakarta.servlet.ServletContext;
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import org.junit.jupiter.api.Test;
+import org.mockito.Mockito;
+
+import java.io.PrintWriter;
+
+import static org.mockito.Mockito.*;
+
+class GetServletContextTest {
+
+    /**
+     * Test that the `doGet` method writes the correct message
+     * retrieved from the ServletContext's init parameter `message`.
+     */
+    @Test
+    void whenDoGet_thenWritesMessageFromServletContext() throws Exception {
+        // Arrange
+        GetServletContext servlet = new GetServletContext();
+        HttpServletRequest mockRequest = mock(HttpServletRequest.class);
+        HttpServletResponse mockResponse = mock(HttpServletResponse.class);
+        ServletContext mockServletContext = mock(ServletContext.class);
+        PrintWriter writer = mock(PrintWriter.class);
+
+        when(mockResponse.getWriter()).thenReturn(writer);
+        when(mockServletContext.getInitParameter("message")).thenReturn("Hello, World!");
+        servlet.init(mock(ServletConfig.class));
+        when(servlet.getServletContext()).thenReturn(mockServletContext);
+
+        // Act
+        servlet.doGet(mockRequest, mockResponse);
+
+        // Assert
+        verify(mockResponse.getWriter()).write("Hello, World!");
+    }
+
+    /**
+     * Test that the `doGet` method handles a null message gracefully
+     * when the ServletContext's init parameter `message` is not set.
+     */
+    @Test
+    void whenDoGet_thenHandlesNullMessageGracefully() throws Exception {
+        // Arrange
+        GetServletContext servlet = new GetServletContext();
+        HttpServletRequest mockRequest = mock(HttpServletRequest.class);
+        HttpServletResponse mockResponse = mock(HttpServletResponse.class);
+        ServletContext mockServletContext = mock(ServletContext.class);
+        PrintWriter writer = mock(PrintWriter.class);
+
+        when(mockResponse.getWriter()).thenReturn(writer);
+        when(mockServletContext.getInitParameter("message")).thenReturn(null);
+        servlet.init(mock(ServletConfig.class));
+
+        when(servlet.getServletContext()).thenReturn(mockServletContext);
+
+        // Act
+        servlet.doGet(mockRequest, mockResponse);
+
+        // Assert
+        verify(mockResponse.getWriter()).write((String) null);
+    }
+
+    /**
+     * Test that the `doGet` method interacts with the ServletContext
+     * to retrieve the `message` init parameter.
+     */
+    @Test
+    void whenDoGet_thenInteractsWithServletContext() throws Exception {
+        // Arrange
+        GetServletContext servlet = new GetServletContext();
+        HttpServletRequest mockRequest = mock(HttpServletRequest.class);
+        HttpServletResponse mockResponse = mock(HttpServletResponse.class);
+        ServletContext mockServletContext = mock(ServletContext.class);
+        PrintWriter writer = mock(PrintWriter.class);
+
+        when(mockResponse.getWriter()).thenReturn(writer);
+        when(mockServletContext.getInitParameter("message")).thenReturn("Test Message");
+        servlet.init(mock(ServletConfig.class));
+        when(servlet.getServletContext()).thenReturn(mockServletContext);
+
+        // Act
+        servlet.doGet(mockRequest, mockResponse);
+
+        // Assert
+        verify(mockServletContext).getInitParameter("message");
+    }
+}

web-modules/jakarta-servlets-2/src/test/java/com/baeldung/servlet/context/ServletRequestTest.java

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+package com.baeldung.servlet.context;
+
+import jakarta.servlet.http.HttpServletRequest;
+import jakarta.servlet.http.HttpServletResponse;
+import mockit.Mocked;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.mock.web.MockServletContext;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+import java.io.StringWriter;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+class ServletRequestTest {
+
+    @Mocked
+    HttpServletRequest request;
+    @Mocked
+    HttpServletResponse response;
+    private ServletRequest servletRequest;
+    private StringWriter stringWriter;
+
+    @BeforeEach
+    void setUp() {
+        servletRequest = new ServletRequest();
+        stringWriter = new StringWriter();
+    }
+
+    @Test
+    void givenHttpServletContext_thenReturnsServletContextParameters() throws IOException {
+        request = mock(HttpServletRequest.class);
+        response = mock(HttpServletResponse.class);
+
+        String message = "Welcome to baeldung!";
+        MockServletContext mockContext = new MockServletContext();
+        mockContext.addInitParameter("message", message);
+
+        when(request.getServletContext()).thenReturn(mockContext);
+
+        when(response.getWriter()).thenReturn(new PrintWriter(stringWriter));
+
+        servletRequest.doGet(request, response);
+
+        assertEquals(message, stringWriter.toString());
+    }
+
+    @Test
+    void givenHttpServletContext_whenMocked_thenReturnsServletContextParameters() throws IOException {
+        request = mock(HttpServletRequest.class);
+        response = mock(HttpServletResponse.class);
+        String message = "Welcome to baeldung!";
+        MockServletContext mockContext = new MockServletContext();
+        mockContext.addInitParameter("message", message);
+
+        when(request.getServletContext()).thenReturn(mockContext);
+
+        when(response.getWriter()).thenReturn(new PrintWriter(stringWriter));
+        servletRequest.doGet(request, response);
+
+        assertEquals(message, stringWriter.toString());
+    }
+
+    @Test
+    void whenNoInitParameter_thenReturnsEmptyResponse() throws IOException {
+        request = mock(HttpServletRequest.class);
+        response = mock(HttpServletResponse.class);
+
+        MockServletContext mockContext = new MockServletContext();
+        // No parameter is added here
+
+        when(request.getServletContext()).thenReturn(mockContext);
+        when(response.getWriter()).thenReturn(new PrintWriter(stringWriter));
+
+        servletRequest.doGet(request, response);
+
+        assertEquals("null", stringWriter.toString());
+    }
+
+    @Test
+    void whenInitParameterIsNull_thenReturnsEmptyResponse() throws IOException {
+        request = mock(HttpServletRequest.class);
+        response = mock(HttpServletResponse.class);
+
+        MockServletContext mockContext = new MockServletContext();
+        mockContext.addInitParameter("message", null); // Explicitly setting parameter to null
+
+        when(request.getServletContext()).thenReturn(mockContext);
+        when(response.getWriter()).thenReturn(new PrintWriter(stringWriter));
+
+        servletRequest.doGet(request, response);
+
+        assertEquals("null", stringWriter.toString());
+    }
+}